1. Field of the Invention
The present invention relates to a mobile terminal. Although the present invention is suitable for a wide scope of applications, it is particularly suitable for enhancing the feel of manipulation of a mobile terminal keypad and minimizing brightness deviation of keypad illumination.
2. Discussion of the Related Art
Generally, terminals can be categorized into mobile/portable terminals and stationary terminals according to a presence or non-presence of portability.
As functions of the terminal tend to be diversified, the terminal is implemented as a multimedia player type equipped with composite functions including picture or video photographing, music or video file playback, games, broadcast reception and the like for example.
A mobile terminal can be provided with at least one user input unit enabling a user to control the mobile terminal. For instance, the at least one user input unit includes a keypad, a touchpad and the like.
As a display provided to a front side of a recently introduced mobile terminal consists of a touchpad capable of detecting a touch input, the display itself is usually used as a user input unit.
Yet, the mobile terminal tends to be provided with a separate keypad for inputting numerals or characters as well as a touchpad.
And, the keypad is provided with a plurality of manipulating buttons having different user inputs assigned thereto and each of the manipulating buttons are normally provided with an illumination function.
Since an independent light source is provided for each of the manipulating buttons provided to the keypad, a corresponding cost is raised. Therefore, the illumination function is preferably provided in a manner that light sources are provided less than the manipulating buttons to share light provided by the light sources.
In order to share illumination by providing light sources of which number is smaller than that of manipulating buttons, it is able to use a light guide film.
The light guide film includes a sheet formed of a transparent material. Laterally incident light experiences total internal reflection to be supplied under each manipulating button.
If the light source is shared using the light guide film, thickness caused by the light source can be reduced smaller than that caused in case of arranging a light source under a manipulating button. Therefore, an overall thickness of a mobile terminal is reduced to provide a slim mobile terminal.
However, when the light guide film is provided under the keypad, if the corresponding manipulating button is pressed, the corresponding pressure is delivered to a dome switch provided under the light guide film. Therefore, a manipulation feel of the manipulating button is degraded. In particular, when a manipulating button is pressed, a user applies a force greater than that used for a case that a light guide film is not used. Therefore, the user may feel fatigue.
Moreover, in case of using a light guide film, a deviation of brightness can be generated in accordance with a position of a manipulating button of a keypad or a distance from a light source.